Voluminous yarn



Unite t States Patent VOLUMINOUS YARN Hans R. Stucki, Summit, N. J., assignor to Celanese Corporation of America, New York, N. Y., a corporation of Delaware No Drawing. Application June 8, 1954 Serial No. 435,357

4 Claims. (Cl. 57-157) This invention relates to voluminous yarn and relates more particularly to a process for the production of voluminous yarn from yarn having a basis of an organic acid ester of cellulose having a high degree of substitution, and to the product produced by said process.

It has previously been proposed to produce voluminous organic acid ester of cellulose yarn, such as voluminous cellulose acetate yarn, by twisting the said yarn, setting the twist therein, and then untwisting the yarn. This process can be carried out as a multistep operation by taking up the twisted yarn in the form of a package, treating the package of, yarn so as to set the twist in the yarn, and then untwisting the yarn. Preferably, however, the processing of the yarn is carried out in a continuous manner, for example, by passing the yarn through a false twist spindle wherein it is first twisted and then untwisted, and treating the yarn during its passage through the false twist spindle so as to set the twist therein. The yarn obtained in this manner has a good bulk and covering power and a soft hand owing to the fact that the individual filaments in the yarn are crimped in an irregular manner.

When this process is applied to cellulose acetate yarns of commerce, i. e. cellulose acetate yarns made from acetone-soluble cellulose acetate having an acetyl value between about 52 and 56% by weight, it is found that a high proportion of the crimp is removed from the filaments in the yarns by the stresses to which said yarns are subjected during their conversion into a fabric as by weaving, knitting, or the like. A further proportion. of the crimp is removed from the filaments in the yarns during the hot wet treatments of the fabrics containing said yarns in the dyeing and finishing of said fabrics as well as in the cleaning and washing of said fabrics during use. This loss in crimp produces a corresponding loss in the bulk and covering power as well as in the hand of the yarn and the fabrics containing the same which is undesirable.

It is an important object of this invention to provide for the production of voluminous yarn from yarn having a basis of an organic acid ester of cellulose having a high degree of substitution, which will be free from the foregoing and other difficulties.

A. further object of this invention is to provide a process for the production of voluminous yarn from yarn having a basis of an organic acid ester of cellulose having a high degree of substitution, which will yield a yarn having a crimp that is highly resistant to removal.

Another object of this invention is to provide a voluminous organic acid ester of cellulose yarn from yarn having a basis of an organic acid ester of cellulose having a high de ree of substitution, which yarn has a crimp therein that is highly resistant to removal.

Other objects of this invention will be apparent from the following detailed description and claims.

l-According to the present invention, a voluminous yarn is prepared from multifilament yarn having a basis of an organic acid ester of cellulose having a high degree of substitution, by twisting and untwisting the saidyarn' 2,869,318 Patented-Ian. 20, 1959 and treating the yarn so as to set the crimp therein. It has been found that the filaments in a voluminous yarn prepared in this manner will retain a substantial proportion of their crimp during the conversion of said yarn into a fabric by knitting, weaving or the like. They will also retain a substantial proportion of their crimp during the hot wet treatments to which the fabrics containing the same are normally subjected during their dyeing and finishing, as well as during their cleaning and washing in use. As a result, these yarns are well suited for the production of fabrics whose bulk and covering power is high compared to their weight, which possesses a soft hand and high elasticity, and which will retain these properties during use. They are especiallywell suited for the production of knitted fabrics particularly in view of the fact that fabrics containing these yarns exhibit a high degree of resilience and retain such resilience even after extended use.

The organic acid esters of cellulose which may be employed in manufacturing the yarn to which this'invention is applicable are those containing fewer than about 0.5 hydro-Xyl groups or preferably fewer than about 0.25 hydroxyl groups per anhydroglucose unit in the cellulose molecules. An organic acid ester of cellulose falling within this class which gives especially valuable results is cellulose acetate having an acetyl value of at least about 57% by weight or preferably at least about 60% by weight. However, other organic acid esters of cellulose falling within this class which may be used include cellulose propionate and cellulose butyrate as well as the mixed esters cellulose acetate formate, cellulose acetate propionate and cellulose acetate butyrate. In the case of the mixed esters, cellulose acetate propionate and cellulose acetate butyrate the free hydroxyl content should be within the range specified and the propionate and butyrate content should not be more than about 30% by weight, to permit the development of crystallinity in the yarns prepared therefrom. These organic acid esters of cellulose may be converted into yarns by conventional spinning techniques, for example, by extruding a solution or dope containing the cellulose ester through a spinnerette into an evaporative medium or into a liquid coagulating medium. The organic acid esters of cellulose may also be converted to yarns by urging the cellulose esters against a heated plate containing spinning orifices therein whereby the esters will be softened or melted and forced through the spinning orifices.

The yarn prepared from such organic acid esters of cellulose is voluminized by twisting ad untwisting the same and treating the yarn so as to set the crimp therein. During the twisting of the yarns there may be inserted into the yarn a twist corresponding to a twist multiplier of from 500 to 1000 with the higher twists giving a product of greater bulk and elasticity. The twist multiplier is equal to the twist in turns per inch multiplied by the square root of the yarn denier. The voluminizing of the yarn may be carried out as a multistep operation by twisting the yarn on a conventional twister, which may be a ring twister, a cap twister, a flyer twister, or the like and taking up the twisted yarn in the form of a package. Thereafter, the packages of yarn are treated as will be described in detail below in order to relax the stresses introduced by the high twist and to develop a high degree of crystallinity and crystalline order in the yarn thereby making the crimp introduced by the high twist permanent. The yarn is then drawn from the package and untwisted on a conventional twister which may be of the type listed above. The untwisting of the yarn may be carried out to remove all the twist from the yarn, or to leave a small amount of twist in the yarn, or the yarn maybe untwisted completely and a small amount of reverse twist inserted therein, all depending on the characteristics desired in the final product.

Preferably, however, the twisting and untwisting of the yarn are carried out as a continuous operation by passingthe yarn through a false twist spindle wherein it is first twisted and then untwisted. During its passage through the false twist spindle the yarn is treated so as to set the twist therein. False twist spindles suitable for carrying out the treatment of the yarn are shown, for example, in U. S. Patents Nos. 2,089,198 and 2,089,199 to Finlayson et al. and in Stoll, application S. No. 376,- 306, filed August 25, 1953. Although it is necessary to relax the stresses in the yarn and to develop a high degree of crystallinity and crystalline order in the yarn in order to make the crimp therein resistant to removal, not all of the crystallinity and crystalline order need be developed in the yarn during the twisting and untwisting of the yarn. Instead, aportion of the treatment to develop crystallinity in the yarn may be carried out during the twisting and untwisting of the yarn, following which the yarn may be treated further as such or in the form of a fabric to develop a high degree of crystallinity and crystalline order therein. Care should be taken, in this case, to hold the stresses imposed on the yarn to a minimum until this further treatment to develop crystallinity and crystalline order has been completed since such stresses will tend to remove crimp from the filaments in the yarn. For example, a yarn in which only a portion of the crystallinity and crystalline order has been developed may be wound into a package under low tension or knitted into a fabric, and the package of yarn or the fabric may be treated further to develop a high degree of crystallinity and crystalline order in the yarn.

The crimp in the yarn is made permanent and the development of crystallinity and crystalline order in the yarn is efifected by heating the yarn to an elevated temperature for a period of time depending on the temperature employed. When the heating of the yarn is carried out in a continuous process using dry heat, the temperature to which the yarn is heated may range from as low as about 150 C. in which case the heating period may range up to about 5 seconds to as high as about 260 C. in which case the heating period may be as short as about 0.5 second. The heating, with dry heat, may, for example, be carried out using heated air or other heated gas as the heating medium, or by using radiant heat from an electric, gas or other heating element. The heating of the yarn may also be carried out by bringing the yarn into contact with a heated surface such as a roll, plate or the like, or by a combination of several of these expedients. The heating of the yarn to develop crystallinity therein may also be carried out using steam or hot water in contact with the yarn as the heating medium. In this case, somewhat lower heating temperatures or shorter heating periods will be adequate to develop a high degree of crystallinity in the yarn. Thus, with steam, the heating temperature may range from as low as about 150 C. in which case the heating period may range up to about 5 seconds, to as high as about 200 C. in which case the heating period may be as short as about 0.5 second. The heating with steam or hot water may, for example, be carried out by passing theyarn through a vessel or chamber into which the heating medium is admitted at the desired temperatures and corresponding pressures.

The heating of the yarn may also be carried out while the yarn contains'a swelling agent or plasticizer, hereinafter called a plasticizer, for the organic acid ester of cellulose- The plasticizer may be incorporated into the yarn when it is. spun, or it may be applied to the yarn either prior to or as a part of the voluminizing treatment. The-use of aplasticizer permits the treatment ofi the yarn to be carried out atlower temperatures and:

with shorter heating periods. Following the treatment of the yarn, the plasticizer may, if desired, be removed from the yarn, for example, by washing the yarn with a solvent for the plasticizer which is a non-solvent for the yarn. Suitable plasticizers for this purpose include, for example, diethylphthalate, dibutylphthalate, tripropylphosphate, tributylphosphate, and trioctylphosphate.

The voluminized yarn prepared in accordance with this invention retains its crimp during all the treatments to which it is subjected in the manufacture of fabrics, in the dyeing and finishing of said fabrics and also in the use of said fabrics. This yarn may be used alone or it may be doubled with other voluminized yarns, or with other yarns that have not been voluminized. It may also be doubled with yarns that may be shrunk by suitable treatment whereby it is possible to obtain products having a unique decorative appearance.

The degree of crystallinity and crystalline order may be readily determined by means of X-ray diffraction studies. The untreated yarn shows a relatively diffuse X-ray diffraction pattern indicating that there is comparatively little crystalline matter in the yarn. After treatment, however, the yarn shows a sharp X-ray diffraction pattern indicating the presence of relatively large amounts of crystalline matter in the yarn.

The following example is given to illustrate this invention further.

Example A multifilament denier yarn of cellulose acetate having an acetyl value of 61.4% by weight is passed through a false twist spindle of the type shown in the Stoll application referred to above. During its passage through the false twist spindle, 55 turns per inch are inserted into the yarn and then removed from the yarn. The yarn is also heated to a temperature of C. for a period of 2 seconds with hot air as it passes through the false twist spindle and is then taken up on a bobbin. The individual filaments in the treated yarn are highly crimped so that the yarn has good bulk and covering power and a soft hand. In addition, the yarn retains these properties substantially unchanged under various stresses. For example, when the yarn, or a fabric knitted from the said yarn, is immersed in boiling water and then removed and dried it retains these properties substantially unchanged.

The X-ray diffraction pattern of the yarn is sharp indicating that it has a high degree of crystallinity and crystalline order. The untreated yarn, on the other hand has a diffuse X-ray diffraction pattern indicating that it has little crystallinity.

The acetyl, propionyl and butyryl values given herein are all calculated as the corresponding acids, namely, acetic acid, propionic acid and butyric acid.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention what I desire to secure by Letters Patent is:

1. Process for the production of voluminous yarn from yarn having a basis of cellulose acetate having an acetyl value of at least about 60% by weight, which comprises twisting and untwisting the yarn, and heating the yarn to a temperature of between about 150 and 260 C. for a period of about at least 5 seconds and at least 0.5 second, respectively, to set the crimp therein, the time and temperature of heating being sufiicient to change the original diffuse X-ray diffraction pattern to a sharp pattern and being sufficient to produce a product which retains its crimp when immersed in boiling water and then removed and dried.

2. Process for the production of voluminous yarn from yarn having a basis of cellulose acetate having an acetyl value of at least about 60% by weight, which. comprises twisting, and untwisting the yarn, and heating the yarn in steam at a temperature of 150 to 200 C. for about 0.5 to 5 seconds to set the crimp therein, the time and temperature of heating being sufficient to change the original diffuse X-ray difiraction pattern to a sharp pattern and being sutficient to produce a product which retains its crimp when immersed in boiling water and then removed and dried.

3. Process as set forth in claim 1 in which the twisting and untwisting are effected in a continuous false twisting of said yarn, and said heating of the yarn takes place during said false twisting.

4. Process as set forth in claim 2 in which the twisting and untwisting are effected in a continuous false twisting of said yarn, and said heating of the yarn takes place during said false twisting.

References Cited in the file of this patent UNITED STATES PATENTS 2,174,607 Taylor Oct. 3, 1939 2,244,832 Finl'ayson et al June 10, 1941 2,517,694 Merion et a1 Aug. 8, 1950 OTHER REFERENCES 

1. PROCESS FOR THE PRODUCTION OF VOLUMINOUS YARN FROM YARN HAVING A BASIS OF CELLULOSE ACETATE HAVING AN ACETYL VALUE OF AT LEAST ABOUT 60% BY WEIGHT, WHICH COMPRISES TWISTING AND UNTWISTING THE YARN, AND HEATING THE YARN TO A TEMPERATURE OF BETWEEN ABOUT 150* AND 260* C. FOR A PERIOD OF ABOUT AT LEAST 5 SECONDS AND AT LEAST 0.5 SECOND, RESPECTIVELY, TO SET THE CRIMP THEREIN, THE TIME AND TEMPERATURE OF HEATING BEING SUFFICIENT TO CHANGE THE ORIGINAL DIFFUSE X-RAY DIFFRACTION PATTERN TO A SHARP PATTERN AND BEING SUFFICIENT TO PRODUCE A PRODUCT WHICH RETAINS ITS CRIMP WHEN IMMERSED IN BOILING WATER AND THEN REMOVED AND DRIED. 